Abstract
A specific antibody elicited against NADPH-cytochrome c reductase inhibited cytochrome P-450- and NADPH-dependent hydroxylation of biphenyl by rodent liver and lung microsomal preparations. The inhibition profiles suggested that both the 2- and 4-hydroxylation of biphenyl were mediated by a common NADPH-cytochrome c reductase (NADPH-cytochrome P-450 reductase) and that the same flavoprotein species operated in liver and lung microsomes of corn oil- or 3-methylcholanthrene-pretreated rats and hamsters. An immunochemically identical NADPH-cytochrome c reductase also apparently functioned in the NADPH-supported metabolism of benzo(a)pyrene and ethylmorphine. NADH supported the microsomal metabolism of benzo(a)pyrene and ethylmorphine in liver and biphenyl in liver and lung, but the maximal rates of reaction were slower than when supported with NADPH. The K m of NADH for biphenyl 2- and 4-hydroxylations in control hamster liver microsomes were approximately 5 m m. Anti-NADPH-cytochrome c reductase globulin inhibited NADH-supported biphenyl 2- and 4-hydroxylase activities in corn oil- or 3-methylcholanthrene-pretreated rats and hamsters, even at NADH concentrations as low as 0.25 m m. These results indicate that the same flavoprotein reductase species which mediated NADPH-dependent biphenyl hydroxylase donated at least one electron for the NADH-supported hydroxylation.
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